Method and machine for manufacturing molded structures using zoned pressure molding

ABSTRACT

A method for manufacturing a molded structure in a press that includes a first mold and a second mold is provided. The second mold has a plurality of pressure actuators, with each pressure actuator capable of independent operation. The method includes the steps of positioning a preform having a thickness in the first mold, placing a quantity of resin adjacent the preform so as to create a resin reservoir, and then selectively actuating one or more of the pressure actuators apply pressure to the resin reservoir to force at least a portion of the resin reservoir to infuse through the thickness of the preform. The method may also include curing the resin-infused preform, and then removing the cured resin-infused preform from the first mold.

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 09/936,874, filed Dec. 28, 2001, entitled “MethodAnd Machine For Manufacturing Molded Structures Using Zone PressureMolding,” which is the national stage filing of PCT/US00/06932, filed onMar. 17, 2000, which claims priority under 35 U.S.C. §119(e) to U.S.provisional application No. 60/124,978, filed Mar. 18, 1999,incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to liquid molding. Specifically,the present invention relates to active control of the liquid moldingprocess and press during mold filling and curing.

[0004] 2. Description of the Related Art

[0005] A brief overview of the techniques that currently dominate theproduction of liquid molded composites will be useful in demonstratingthe benefits of the process of the present invention. Conventionalprocesses that are most similar in capabilities to the present inventionare: compression molding of Sheet Molding Compound (“SMC”), ResinTransfer Molding (“RTM”), and Structural Reaction Injection Molding(“SRIM”).

[0006] The SMC process typically starts with a sheet of unsaturatedpolyester resin filled with various thickeners and reinforced withchopped glass. The sheets are cut and placed in a heated tool andcompressed at temperatures ranging from 140-200° C. (280-390° F.) andpressures ranging from 7-14 MPa (1000-2000 psi) down to as little as 1.4MPa (200 psi) for new low pressure formulations. As the sheets areheated and compressed, the viscosity drops and the material flows alongthe contours of the mold, typically curing in about 2 minutes. The SMCprocess differs from liquid molding techniques in that the resin andfibers are premixed in a separate operation. The primary advantage ofthe SMC process is that a preform does not have to be constructed. Theprimary disadvantages of the SMC process are its relatively long cycletimes and low strength to weight ratios of the resulting parts.

[0007] In a typical RTM process, a fiber preform is placed in matchedtooling, compressed, and low viscosity statically mixed reactants areinjected into the cavity through single or multiple ports at pressuresranging from vacuum driven to 1.4 MPa (200 psi). As the resin frontprogresses, it forces out any entrapped air through one or more ventsplaced in the matched tooling. After the resin begins to flow out of thevents, the vents are closed and the part is allowed to cure, typicallyfrom 4 to 30 minutes, depending on the part size, part geometry, thenumber and placement of ports, and the specific resin system. A diagramof the RTM process appears in FIG. 1 below. In general, tooling andenergy costs are low for the RTM process, but its high cycle timesreduce manufacturing volumes. The main drawback of the RTM process, as amass production technique, is its fill time.

[0008]FIG. 2 shows that the SRIM process is similar to the RTM process,with the primary exceptions being that the resin is impingement mixed atvery high pressures 100 MPa (1000 bar) and then injected into a heatedtool at pressures ranging from 0.5-1.7 MPa (70-200 psi). The resinsystems used in the SRIM process react very quickly and can cure in aslittle as 45 seconds. To allow mold filling before the resin gels, thepreforms usually do not exceed a 30% volume fraction. The SRIM processhas generally been employed with better quality molds, injectionequipment, and process control than available for the RTM process. Thesefactors have led to a distinction between the two processes; the RTMprocess as a slow, inexpensive technique producing very strong parts vs.the SRIM process as a more sophisticated and expensive method for thevery rapid production of non-structural components. In reality, thedifferences between the processes are slight. The SRIM process is simplythe RTM process using reaction injection molding, typically in a higherquality, heated mold.

[0009]FIG. 3 schematically shows the progression that the resin fronttakes as it infuses a part in the RTM and SRIM processes. Typical timesfor injection, for example, into a preform with a 40% fiber volumefraction, are noted. If the resin is forced too quickly through thepart, air bubbles may be trapped or the fibers of the preform may bedisplaced, degrading the properties of the part. Alternatively, changingthe flow path, for instance, by infusing the resin from the center ofthe part out to the edges, is difficult and may result in nonuniformproperties. In general, the resin flow path is the limiting factor inreducing the cycle time of these techniques.

[0010] In “Study on Compression Transfer Molding (CTM)” published in theJournal of Composite Materials, Vol. 25, No.16,1995, Young and Chiudescribe the CTM goal to be “impregnation through the thicknessdirection.” In their test apparatus they left the mold halves slightlyopen and injected resin into the cavity at various pressures andrecorded filling time. If the mold was not opened enough, the fiberpreform merely decompressed somewhat, still impeding the flow of theresin. Once the proper opening distance was determined, mold fill timesdropped by 37-46% over RTM at the same injection pressure. The proposedmechanism for this was a channel flow between the preform and mold. Themold is then closed, completing infusion in the thickness direction veryquickly with minimum disturbance of the fibers. The strength and modulusof the completed part was shown to be the same as an RTM part. Thelimitation of CTM is that the preform is not rigidly held in placeduring injection and does not create a true open channel for resin toflow through, limiting the maximum rate at which injection can occur.The lowered flow resistance RTM process is still very helpful,especially when infusing very large planar parts like automobile bodypanels. It should also be noted that if very high fiber volume fractionsare sought, the amount of resin injected into the mold is not enough todistribute throughout the mold, and compression times must be lengthenedto allow time for some of the resin to flow through the in-planedirection. The Dodge Viper used a version of CTM called InjectionCompression System (ICS) for many of its components, but as yearlyvolumes were low, cycle times could be as long as 15 minutes. Partfinish was not perfect, but this may have been a problem with otheraspects of the process such as resin system, release agents, etc.

[0011] Another innovative process that attempts to infuse primarilythrough the thickness direction is the patented Seemann Composite ResinInfusion Molding Process (“SCRIMP”). This is a variation on RTM withvacuum assist under a flexible tool, so only one hard mold surface isrequired. The resin is channeled through a high permeability“distribution medium” placed between the tool surfaces and the preform.A vacuum is pulled on the preform and the resin is introduced into andquickly distributed through the medium. The resin then infuses into thepart through the thickness direction, creating a very uniform, highvolume fraction part. A porous peel ply is placed between thedistribution medium and the preform so that it can be removed anddisposed of. The process has proven extremely popular for infusing huge,planar parts like large boat hulls and railway cars. SCRIMP works well,but as a vacuum driven process, it is too slow and also generates toomuch scrap to be considered for mass production. Seemann has anotherpatent (U.S. Pat. No. 5,601,852) which details a variation of thethrough thickness approach used in SCRIMP that employs physical channelsin a flexible, molded outer tool surface. The tool can, unlike thevacuum bag distribution medium, be quickly cleaned and reused, but willstill not generate the cycle times or scrap levels required for massproduction.

[0012] Another interesting RTM-like system developed by James et al. ofthe Northrop Corporation is detailed in U.S. Pat. No. 5,204,042. Thisprocess attempts to avoid the maximum fiber volume limitation of RTM,quoted as “50-60% by weight” (presumably for glass) by sandwiching anelastomeric pad made of Dow Silastic® E silicon rubber between moldsurfaces. The pad expands when heated, compressing the fiber at up to“75-80% by weight.” The part is infused under lower compaction and thencompresses tremendously when heated for curing. This speeds infusionwhile providing a very high quality part. Like SCRIMP, only one tooledmold surface is needed, but a very rigid upper mold section is required.

[0013] The trend in RTM-like processes is toward through-thicknessinfusion. CTM, SCRIMP and other variants achieve superior results totraditional liquid molding with their modifications. But each must tradesomething for its gains. CTM decreases mold filling times, but is stillsensitive to the volume fraction of the preforms. SCRIMP works well evenwith high volume fractions, but is limited in speed by using vacuumpressure to drive infusion. The Northrop process delivers improved moldfilling and very high volume fraction, but is still limited by itsin-plane infusion path.

[0014] An important factor in many modern processing machines is theamount of control that can be exercised over the process. The advent ofmodern computer technology has allowed the development of remoteinput/output systems that communicate over one wire and have verysophisticated programming and diagnostic tools. These systems have beenfinding their way into more and more industrial applications and willsomeday displace all current PLC based controllers as well asintroducing sophisticated computer control where it has never beenbefore. Although there are many different protocols in the market, theindustrial control market and the personal computer market have beengetting together to create some software and communication standards.Even today there is a vast range of hardware and software solutions frombasic on/off control of a motor to running entire plants.

[0015] Each of the known processes have limitations that prevent themfrom being used to produce structures that exploit the full potential ofcomposite material design. The SMC process has a very low cycle time,but it is restricted to relatively low fiber volume fractions with shortfiber lengths, reducing the specific strength of the part. The RTMprocess can operate with higher fiber volume fraction preforms, but theresin typically must flow through the plane of the preform and thehigher the fiber volume fraction, the lower the permeability, and themore difficult and time consuming the resin flow step becomes.Variations of the RTM process have attempted to solve the resin flowproblem by using multiple, staged injection ports, but process controlcan be very difficult and each mold must be painstakingly optimized. Inthe SRIM process the flow rates are even higher to allow the use offaster curing impingement mixed resins, such as polyurethanes. Therequired faster flow rates limit the maximum fiber volume fraction to alevel well below the level for optimizing the properties of the part.These known methods have achieved production-ready cycle times, but thetrade-off for this is a low fiber volume fraction, resulting in a partwith extra resin that adds unnecessary weight and cost.

[0016] The ideal liquid molding process is one which: (1) can easilyinfuse very high

[0017] fiber volume fraction preforms thereby maximizing the physicalproperties of the resulting part and minimizing the cost of resins; (2)can offer very low cycle times thereby enabling large volume productionsas cheaply as possible; (3) can use inexpensive tooling and processequipment; and (4) can quickly, easily, and cost-effectively accommodatesmall production runs.

SUMMARY OF SOME OF THE ASPECTS OF THE INVENTION

[0018] The advantages and purposes of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention.

[0019] To attain the advantages and in accordance with the purpose ofthe invention, as embodied and broadly described herein, the zonedpressure molding press and process, in a first aspect, encompasses amethod for manufacturing a molded structure in a press that includes afirst mold and a second mold. The second mold has a plurality ofpressure actuators, with each pressure actuator capable of independentoperation. The method includes the steps of positioning a preform havinga thickness in the first mold, placing a selected quantity of resin inthe first mold, thereby creating a resin reservoir, and then selectivelyactuating one or more of the pressure actuators to force at least aportion of the resin reservoir to infuse through the thickness of thepreform. The method also includes curing the resin-infused preform, andthen removing the cured resin-infused preform from the first mold. Afterthe step of positioning, a top cover may be placed upon the preform. Thetop cover may be sealed to the first mold with one or more of thepressure actuators. Alternatively, the top cover may be sealed to thefirst mold by a mechanical clamping device. The resin reservoir may beformed between the top cover and the preform. The step of selectivelyactuating one or more of the pressure actuators may include a computerfor controlling the pressure actuators. Moreover, the computer maycontrol the pressure actuators at least partially in response to a firstsensor. The first sensor may be a pressure or temperature sensor.

[0020] In a second aspect, the invention encompasses a method formanufacturing a molded structure in a press that includes a first moldand a second mold. The second mold has a plurality of pressureactuators, and each pressure actuator is capable of independentoperation. The method includes the steps of placing a selected quantityof a raw material into the first mold, thereby creating a raw materialreservoir, and selectively actuating one or more of the pressureactuators to force at least a portion of the raw material reservoir toconform to the first mold. The method also includes curing the rawmaterial, and removing the cured part from the first mold. Before thestep of placing, a preform having a thickness may be positioned into thefirst mold, and the step of selectively actuating thereby forces the rawmaterial to infuse through the thickness of the preform.

[0021] In a third aspect, the present invention encompasses a machinefor manufacturing a molded part formed from raw material that is moldedand cured. The machine includes a first mold and a second mold. Thefirst mold is for holding the raw material while the raw material ismolded and cured and for defining a first surface of the molded part.The second mold is for defining a second surface of the molded part. Thesecond mold has a plurality of pressure actuators, each pressureactuator capable of acting substantially independently upon the rawmaterial while the raw material is being molded. Each pressure actuatormay be capable of acting substantially independently upon the rawmaterial while the raw material is cured. Additionally, a controller mayactively control the plurality of pressure actuators. Moreover, one ormore first mold sensors may be incorporated into the first mold, wherebythe controller receives feedback from one or more of these first moldsensors. Further, one or more pressure actuator sensors may beincorporated into one or more of the plurality of pressure actuators,whereby the controller receives feedback from one or more of thesepressure actuator sensors. The controller may include a computer.

[0022] In a fourth aspect, the present invention may encompass a methodfor molding a top cover from raw material, the top cover for use in amachine for molding a part. The machine has an upper and lower mold, theupper mold having a plurality of pressure actuators, and each pressureactuator capable of independent operation. The method includes the stepsof positioning a prototype part having a top surface in the lower mold,placing the raw material onto the top surface of the prototype part,actuating at least one of the plurality of pressure actuators to contactthe raw material, and curing the raw material. Additionally, the step ofactuating may include the at least one pressure actuator applying agiven pressure to the raw material. Alternatively, the step of actuatingmay include the at least one pressure actuator being displaced aprescribed distance. Moreover, prior to the step of placing, each of theplurality of pressure actuators may be lowered into contact with the topsurface of the prototype part and the plurality of pressure actuatorsmay be raised such that each pressure actuator maintains a constantposition relative to the other pressure actuators. Even further, thestep of actuating may include lowering the plurality of pressureactuators such that each pressure actuator maintains a constant positionrelative to the other pressure actuators.

[0023] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory only and are not restrictive of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate several embodimentsof the invention and together with the description, serve to explain theprinciples of the invention.

[0025]FIG. 1 is a schematic illustration of the RTM process.

[0026]FIG. 2 is a schematic illustration of the SRIM process.

[0027]FIG. 3 is a schematic illustration showing the progression that aresin front takes as it infuses a part in the RTM and SRIM processes.

[0028]FIG. 4a shows an exploded view of an embodiment of the presentinvention.

[0029]FIG. 4b shows an example of a pressure actuator.

[0030]FIGS. 5a-9 show a typical progression of the process of thepresent invention.

[0031]FIG. 10 shows a stepped top cover in situ.

[0032]FIG. 11 is a schematic of a hybrid pneumatic/hydraulic actuatorsystem.

[0033]FIG. 12 shows how the Interbus® controller card and output moduleare connected to the valve system to allow computer controlled switchingbetween two regulated pressures.

[0034]FIG. 13 is a schematic of a zoned pressure molding press setup.

[0035]FIG. 14 is a diagram of the distinct layers formed by the bus andpress component classes, and the usage relationships between theclasses.

[0036]FIG. 15 is an example of a Press Control Panel from theuser-interface.

[0037]FIG. 16 is an example of a tool design incorporating nested zoneswith sliding seals.

[0038]FIG. 17 is an example of a detail of a seal design.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Reference will now be made in detail to the present preferredexemplary embodiments of the invention, which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

[0040] The current invention improves on the state of the liquid moldingart by, among other things, providing an order of magnitude reduction inmold filling times, and providing for much greater levels of processcontrol.

[0041] Process Overview

[0042] The present invention avoids the shortcomings of other liquidmolding processes and presses by taking a different approach to theinfusion of a fiber preform. Rather than injecting resin through thein-plane direction, as in the RTM and SRIM processes, the process andpress 10 of the present invention distribute the resin over the surfaceof the part under active control, then force it through the thicknessdirection. This drastically reduces fill times without disturbing fiberorientation, allowing the use of both high volume fraction preforms(60%+) and rapidly curing resin systems, such as thermosets, in the sameprocess. The zoned pressure molding technique of the present inventionprovides full control over the flow of the resin.

[0043] As depicted in FIGS. 5a-9, the zoned pressure molding process ofthe present invention utilizes a lower mold 20 into which raw material22 for molding is placed. Typically, the raw material 22 includes afiber preform 24 and resin 34, although the raw material 22 may includejust the resin 34. Moreover, the resin 34 need not be a singlecomponent, but may include fillers and/or binders of any of a variety ofmaterials. An upper mold assembly 26 is provided for applying pressureon the surface of the raw material 22. The upper mold assembly 26includes an array of pressure actuators 28. Each of these pressureactuators 28 may apply pressure to a specific portion or zone 30 of theraw material 22 in the lower mold 20. A top cover 32 may be placed overthe raw material 22. By controlling the pressure applied by theindividual pressure actuators 28 on each of the zones 30, completecontrol of the pressure distribution on the raw material 22 may beachieved both during the mold filling process and during cure.

[0044]FIGS. 5a-9 show a typical progression of the zoned pressuremolding process of the present invention. In FIG. 5a, the preform 24 isloaded into the mold 20, the top cover 32 is sealed, and a vacuum isdrawn on the part. The pressure actuators 28 are then actuated to createadditional pressure on the preform 24. In FIG. 5b, one or more centralzones 30 a are left uncompressed by the pressure actuators 28 and aquantity of resin 34, preferably a carefully metered quantity of resin,is injected through the top cover 32 into these uncompressed zones. Thebubble of resin 34 that forms between the preform 24 and the top cover32 is then used as a reservoir 36 for infusing the preform 24. Thepressure on the central zones 30 a is progressively raised, forcingresin 34 through the thickness of the preform 24 in this area.Typically, the pressure on the central zones 30 a is raised while thepressure on the adjacent zones 30 b is maintained at a relatively highlevel. This forces the resin 34 to travel through the thickness of thepreform 24 in the central zones 30 a, and inhibits the travel of theresin 34 into the adjacent zones 30 b. When the central zone 30 a hasbeen infused through the thickness, the pressures on the adjacent zones30 b are reduced and the pressures on the central zones 30 a are raisedto full, forcing the reservoir 36 to flow into the adjacent zones 30 bas shown in FIG. 6. The result is a relatively, very rapid flow of resin34 from one zone to another. Also, as compared to prior known liquidmolding processes, as the resin 34 flows into the preform 24, it does soover a much larger area primarily through the thickness direction. Thecycle is repeated until the resin 34 has reached the perimeter of thetop cover 32 (FIG. 7). Once the preform 24 is completely infused (FIG.8), the part 38 is allowed to cure and the finished part 38 is removedfrom the mold 20 (FIG. 9). In this manner, the process of the presentinvention could allow a theoretical reduction in mold filling time of atleast an order of magnitude.

[0045] The zoned pressure molding process and press 10 of the presentinvention also provide some additional features that are useful incontrolling part quality. During infusion, converging resin 34 flowfronts can cause weld lines or create voids in a part. The process ofthe present invention can eliminate or reduce these weld lines and voidsby cycling the pressure actuators 28, i.e., controlling individualpressure actuators or groups of pressure actuators so as to vary thepressure applied to specific zones 30. By cycling the pressure actuators28, the resin 34 in these zones can be thoroughly mixed. Thus, after theinitial infusion of resin 34, the pressure actuators 28 could set up akneading cycle that creates micro flows in the resin 34 throughout thepreform 24, insuring complete fiber wet-out. Also, for instance,preforms with widely varying thicknesses and/or porosities could beinfused without concern for the irregular shape of the resin front. Apressure actuator control algorithm for any specific given part could bedeveloped to accommodate any necessary or preferred flow regime.

[0046] Top Cover

[0047] The top cover 32, which may provide the upper mold surface 40,transmits the forces applied by the pressure actuators 28 to the preform24 set into the lower mold 20. The top cover 32 typically needssufficient flexibility to accommodate the zoned action of the pressureactuators 28, and yet sufficient stiffness to accommodate the transitionareas between zones 30. The lower surface 42 of the top cover 32 ispreferably molded to the shape of the preform 24. In operation, the topcover 32 is placed over the preform 24, and preferably sealed, onto thelower mold 20. Because the top cover 32 is flexible, it can deform toaccommodate flow of resin 34 over, instead of through, the preform 24when the pressure actuators 28 are released or partially released.

[0048] The top cover 32 could be made such that the upper surface 44 ofthe top cover 32 is stepped, i.e., the upper surface 44 could beprovided with multiple pressure actuator contact zones or steps 46, eachstep being perpendicular to the axis of actuation of the pressureactuators 28 (see FIG. 10). The lower surface 42 of the top cover 32forms the upper mold surface 40, and thus, the lower surface of the topcover 32 would typically be contoured to the shape of the desiredfinished part 38. Each pressure actuator 28 could be provided with asubstantially flat-bottomed pad 48 for applying force to one of thesteps 46 on the upper surface 44 of the top cover 32, regardless of theshape of the lower surface 42. This approach to the construction of thetop cover 32, i.e., providing a quasi-generic stepped upper surface 44to the top cover 32, would allow the design or setup of the press 10 tobe essentially independent of the shape of the parts to be molded,thereby providing the flexibility to sequentially run different moldsthrough the same press.

[0049] One possible scenario for actual manufacture of such a top cover32 would start with insertion of a prototype part 50 into the lower mold20, to enable the lower surface 42 of the top cover 32 to be defined.The pressure actuators 28 could then be lowered to the prototype's uppersurface, locked in place, and the upper platen 60, with the lockedpressure actuators 28, could be raised to create a gap between theprototype part 50 and the pressure actuators 28. The selected top covermaterial would then be poured, injected, laid, or otherwise placedeither directly or indirectly onto the prototype part 50 in the lowermold 20. The upper platen 60, with the pressure actuators 28 stilllocked in place, could then be lowered to a position equal to itsoriginal position minus the desired top cover thickness, and the topcover material would be allowed to cure.

[0050] Another possibility for manufacturing a stepped top cover 32would start at the mold design level. For instance, software, such asCAD/CAM software, which might be used to design the mold itself couldhave a feature, selected when the mold is ready to be machined or setup,that would automatically design a separate block with the properpressure actuator step profile for the upper surface 44 of the top cover32. This profile could then be machined from an inexpensive toolingmaterial, and used as a mold for the upper surface 44 of the top cover32.

[0051] Alternatively, for a variety of reasons, it may be preferred touse a top cover 32 that does not have a stepped upper surface. Forinstance, variations in the thickness of the steps 46 could cause thelocal stiffness of the top cover 32 to vary by an unacceptably largeamount. Such stiffness variations might prevent the uniform deflectionof the top cover 32 that would normally allow the resin reservoir 36 tobe moved from zone to zone. In this case, the pads 48 of the pressureactuators 28 could be designed to more nearly conform to the desiredshape of the finished part 38. Manufacturing or forming the top cover 32could be similar to that described above, but neither the pressureactuators 28 need be locked in place nor a pressure actuator stepprofile block need be used to mold the upper surface 44 of the top cover32. Instead, since the pads 48 of the pressure actuators 28 would nearlyconform to the top surface of the part 38, the top cover 32 would have asubstantially constant thickness, and the top cover material need onlybe laid onto the prototype part to a desired thickness. Indeed, in someapplications, the top cover 32 would only need to be a thin flat sheetto aid in sealing the mold, and in such instances, a material such asthin, flat, elastomeric sheets could be used to form the top cover 32.Even further, such an elastomeric material be could supplied in apartially cured state, which would then conform to the preform 24 forthe final cure. Conversely, if a mold, as described above, is desired toaid in forming the upper surface of the top cover 32, it could bedesigned/machined directly from the CAD/CAM software.

[0052] Also as described above, the pads 48 of the pressure actuators 28could be manufactured to conform or nearly conform to the top surface ofthe finished part 38.

[0053] This could be accomplished by casting and curing the pad materialonto a prototype part in the mold, and then cutting the pad materialinto the proper number of pieces.

[0054] In even another possible construction, the pads 48 of thepressure actuators 28 and the top cover 32 could be formed as anintegral unit. This configuration might be especially applicable ifthere are no abrupt changes in the curvature of the finished part 38,the range of motions of the pressure actuators 28 during the resininfusion steps are small, and the attachment of the pads 48 to thepressure actuators 28 allows a certain degree of tilt or play. As withthe manufacture of the conforming pads described above, the integralpads 48/top cover 32 could be cast onto a prototype part in the mold andcured in situ. With the integral pads 48/top cover 32 attached to thepressure actuators 28, the pressure actuators 28 would be limited tovery small relative motions.

[0055] The main focus of top cover material selection is ensuring enoughflexibility to provide for a sufficient resin reservoir 36, while havingenough stiffness to allow for a continuous pressure profile betweenadjacent zones 30. The stiffness must also be high enough to preventundesirable deforming or smearing of the top cover 32 when curvature ofthe molded part is high. Furthermore, the large number of cyclesrequired for production requires a top cover material that is fatigueand wear resistant. Additionally, the nature of the liquid moldingprocess requires a high maximum temperature and the capability to handlerepeated thermal cycling. Compatibility with the many different resinsystems used in the liquid molding process must also be considered whenselecting a top cover material. Finally, candidate materials that areonly available in sheet form must be flexible enough to conform to areasof high curvature, as well as to deform properly around any inserts, asdiscussed below. The flexible top cover 32, which forms the upper moldsurface 40, could be constructed with a fiber reinforced elastomer orrubber modified vinylester.

[0056] In most situations, it may be desirable to seal the top cover 32to the lower mold surface 62. Two alternative methods for providing sucha seal are presented. A first option could be to have a mechanism pressthe top cover 32 to the lower mold 20 around the edges of the mold. Sucha mechanism, for instance, could be actuated by pneumatics, similar tothe pressure actuators. Another option could be a simple mechanicalclamp. In one aspect, the top cover 32 could be rigidly connected to theupper platen 60, sealing the upper mold assembly 26 to the lower mold 20as the platen 60 is lowered into position. The actual sealing element 64could be formed from the top cover material itself or from separateplates, gaskets, o-rings, nubbins, etc. Furthermore, the method used toseal the top cover 32 to the lower mold 20 could also allow fornet-shape part molding, i.e., the molding of finished parts 38 that donot require trimming.

[0057] In most instances, the top cover 32 will also be required toinclude or interface with a variety of fixtures 66 (see FIG. 13),including (but not limited to) injection nozzles, vacuum and otherinserts, sensors, part release inserts, and caul plates.

[0058] Finally, it may be desirable to include temperature control intothe top cover 32. Temperature control may be accomplished, among otherways, through choice of material. For instance, the top cover materialmay include additives such as chopped fibers. Alternatively, the topcover 32 may be composed of multiple layers of one or more materials,including, for instance, a possible metallic layer. Temperature controlmay also be accomplished by having a top cover 32 that is substantiallythermally transparent (i.e. thin). Furthermore, active temperaturecontrol may be incorporated into the top cover 32. In some instances,electrical heating of the top cover 32 may be the best option.

[0059] Sliding Zone Seals

[0060] Alternatively, instead of using top cover 32 to contain the resinand seal against vacuum, another option is to use seals 52 locatedbetween the sliding portions 54 of actuators 28. Sliding portions 54 ofactuators 28 could include, for instance, transfer plates 70 or pads 48.Sliding portions 54 of actuators 28 may be machined and positioned witha controlled gap between adjacent sliding portions. Channels 56 forseals 52 may be machined into the sides of sliding portions 54 such thatthe seals are captive during all relative motions of the slidingportions 54. At the outer boundaries of the array of actuators 28 orsliding portions 54, a captive or stationary portion 58 may be providedas a surface for the outermost sliding portions 54 to seal against. FIG.16 shows an embodiment wherein a series of nested sliding portions 54are provided with seals 52. Part A is the cavity of the tool, upon whichpart B contacts with an unmoving face seal. The inside surface of part Bprovides a sealing surface for part C, within which parts D and E nest.Seal channels 56 are machined into the outside face of parts C-E. Afterassembly, parts B-E remain together, moving relative to each other byonly a small amount during actuation, so that the alignment of seals 52is not disturbed. The individual sliding portions 54 may be actuated byhydraulic or other means and may also be stabilized by external orinternal bearings or bushings.

[0061] The tighter tolerances that may be required to provide aconsistent gap between the sealing surfaces increase the price of thetool, but sliding seals 52 may offer several advantages at higherproduction volumes. Wear on top cover 32, due to chemical, thermal, andphysical stresses, may be eliminated. Further, top covers made fromsilicon-based materials should not be exposed to epoxy resins forlengthy periods of time since the amine curing agents tend to embrittlethe silicon. Additionally, top covers 32 may have relatively largecoefficients of thermal expansion (CTE). Any mismatch of the CTE of topcover 32 to the rest of the tool may either impart undesirable physicalstresses when installed at room temperature or risks the possibility ofwrinkles inside the tool at elevated temperatures. While these issuesmay not be a problem at low production volumes, the reduced maintenanceassociated with the use of a sliding seal may be attractive ifproduction volumes are increased. It may also be possible to increasethe working temperature of the mold well above the operating range ofavailable top cover materials, which may be helpful when faster cycletimes are required.

[0062] Additionally, without the use of the elastomeric surface of thetop cover, actuators 28 and/or transfer plates 70 may provide a morecontrolled surface finish to the that side of the part. Actuators 28 maybe simply machined and polished to the appropriate finish and directlyact as the surface of the tool. Although there may be small zone witnesslines, these residual marks should not be much larger than normalplastic parting lines, which are easily deflashed. More precisethickness control over the part could also be achieved since the thermaland mechanical distortion of the relatively soft top cover would nolonger be a factor.

[0063] A variety of sealing methods are appropriate for thisapplication. For instance, seal selection could depend on the bend radii(which is related to the zone geometry), the operating temperature andpressures, and the desired chemical resistance.

[0064] Standard elastomeric O-rings may be appropriate for creating avacuum tight seal, and may, in some cases, be appropriate for primaryresin seals. Standard solid polymeric seal materials such as Teflon,either spring or elastomer energized, could provide excellent chemicalresistance and sufficient life at elevated temperatures. Braidedcompression seals infused with polymer could also be utilized. Where thegeometry of the seal is complex or of tight radius, hollow elastomericseals pressurized by a gas could be used to preload a polymeric orbraided seal or as the primary seal. By maintaining the preload on theseal with gas pressure, the effects of varying tolerances caused by wearor geometry would be minimized. FIG. 17 shows the detail of a sealdesign with an upper o-ring vacuum seal 55 and a primary Teflon resinseal 57 energized with another elastomeric o-ring 59.

[0065] Pressure Actuators

[0066] An array of pressure actuators 28 is provided to selectivelyapply pressure to specific portions or zones 30 of the preform 24 orpart being molded. These pressure actuators 28 may consist of pneumatic,hydraulic, electrically, or electromagnetically actuated systems, eachof which applies pressure to a specific portion or zone 30 of thepreform 24, typically via a pressure transfer plate 70. Preferably, thearray of pressure actuators 28 is computer-controlled.

[0067] The array of pressure actuators 28 would typically be attached toa platen 60, and raising or lowering the platen 60 would raise or lowerthe array of pressure actuators 28. Thus, for instance pressure could beapplied to the preform 24 by locking out any motion of each individualpressure actuator 28, and then simply lowering the platen 60.Alternatively, pressure could be applied to the preform 24 by lockingout any motion of the platen 60, and then actuating one or more of theindividual pressure actuators 28.

[0068] At the lower end of each pressure actuator 28 is typicallyprovided a transfer plate 70. The transfer plate 70 may be rigidlyattached to the pressure actuator 28, or the attachment may provide forone or more degrees of freedom. For instance, it may be desirably insome applications to attach the transfer plates 70 to the pressureactuators 28 via ball joints. Furthermore, if one or more degrees offreedom are provided for in the attachment, resistance to one or more ofthe allowed movements may be desirable. For instance, the ball jointsmay be preloaded.

[0069] The size, shape, and material of the transfer plates 70 aregoverned by, among other things, the geometry of the upper surface ofthe finished part 38, the possible need for complementary aligning ofthe edges of adjacent plates 70, including for instance, possiblyinterlocking edges, heat transfer and or thermal expansionconsiderations, and the required pressure to be applied to the preform24. If the top cover 32 is stepped, as described above, the transferplates 70 of the pressure actuators 28 might only need to be simpleblocks, possibly machined out of aluminum or steel. If, however, the topcover 32 is not stepped, then the transfer plates 70 would preferablyconform, or nearly conform, to the upper surface 44 of the top cover 32.

[0070] Alternatively, pads 48 that nearly conform to either the uppersurface 44 of the top cover 32 or the top surface of the preform 24, ifa top cover is not required, could be attached to essentially flattransfer plates 70. For instance, the pads 48 could be elastomeric padsthat are glued, or otherwise fastened to the transfer plates 70. Astepped pad sheet could be molded in a manner similar to themanufacturing method described for the stepped top cover 32 above. Thispressure actuator stepped pad sheet could then be cut into theindividual pressure actuator pads 48, each of which would be glued to aflat transfer plate 70.

[0071] The stiffness of the pad material should be such that deformationof the pad 48 during the application of pressure to the preform 24 ormolded part 38 does not result in inter-zone interference. Fatigue,wear, and thermal transfer properties are, as always, considerations inthe materials selection process. Moreover, if during pressure cycling,the pads 48 rub against one another as the actuators 28 are raised andlowered, then the sliding friction between the pads must be minimized.Finally, the necessary tolerances or allowances between zones 30 may beinfluence by process requirements as well as top cover stiffnessconsiderations. For instance, high temperature processes might requireadditional clearances to account for thermal expansion of the pads 48.

[0072] In some applications, it may be desirable to provide a mechanicallocking interface between the pressure actuators 28. This lockinginterface would keep the pressure actuators 28 properly spaced and linedup, and further, could allow the pressure actuators to share side loadscaused by mold curvature, as discussed below, and preloading of thepressure actuators, among other things.

[0073] It might also be desirable in some applications to providetemperature control of the pressure actuators 28, including possibletemperature control of the pressure actuator transfer plates 70 and pads48. Such active or passive temperature control of the transfer platesand pads could be provided in addition to, or instead of, anytemperature control provided for the top cover 32. Temperature controlof the pressure actuators 28 could allow for zoned temperature control,which may be desirable for the greater degree of control it providesover the infusion and curing process. In addition, the physicalincorporation of temperature control mechanisms may be considerablyeasier in the pressure actuators 28, than when compared to the thinnertop cover 32. A thermally transparent top cover 32 would enhance thecontribution of any temperature control applied to the pressureactuators 28.

[0074] Any of a great variety of sensors 72, most particularly pressureand temperature sensors that would aid in controlling and monitoring theinfusion and curing process, could be attached to the pressure actuatortransfer plates 70, or, possibly more easily, molded into the pressureactuator pads 48.

[0075] The pressure actuators 28 must have sufficient travel to enablethe top cover 32 to deflect enough to let the resin reservoir 36 fill.The amount of required travel depends upon, among other things, thestiffness of the top cover 32, the pressure applied to the preform 24,the size and shape of the pressure actuator 28, and part size andgeometry. For instance, a stiffer top cover 32 would require less travelof the pressure actuator 28 than would a more flexible top cover 32. Alarge reservoir 36 may be desirable on a large part to shuttle resin 34around, so a more flexible top cover 32 and greater actuator travel maybe required. Furthermore, the pressure actuator 28 must have sufficienttravel to adequately compress the preform 24 to its final desired fibervolume fraction.

[0076] The pressure actuators 28 will typically be mounted to an upperplaten 60. The entire upper mold assembly 26 (including upper platen,pressure actuators, transfer plates, pads and top cover, if any, etc.)must be moved up at the end of each curing cycle to allow for part 38removal. This raising and lowering of the upper mold assembly 26 may bedone with an electrically-actuated ball screw, or a similar arrangement.

[0077] A production line incorporating the process of the presentinvention could consist of several lower molds 20 that are prepared andloaded outside the press 10, rotated into the press 10 for infusion andcuring, then rotated out for part removal. In this case, a conveyancesystem would need to be created to move the lower mold 20 and preform 24assemblies, including automatic connection of any heating/cooling lines,as well as automatic alignment of the lower mold and preform assemblywith the upper mold assembly 26.

[0078] In a high volume production situation, a quick release system 74that disconnects any control lines, heating/cooling lines, wires orother such lines from the pressure actuators 28, thereby facilitatingthe release of the actuators 28 from the platen 60 could ease repair andmaintenance of the pressure actuators 28. Furthermore, for a press 10that is to be used with a wide variety of molds, the capability toquickly and easily replace the pressure actuators 28, thereby adjustingthe travel and/or load capacity of the system, is very attractive.Alternatively, providing pressure actuators 28 capable of beingindividually adjusted in situ could also be desirable. For instance, afriction and/or groove-based system, similar in operation to tongs forcarrying steel ingots, could work effectively for adjusting the heightsof the individual actuators 28. The adjustment could be done either atthe mounting of the pressure actuator 28 to the platen 60 or in aconnecting rod between the cylinder of the pressure actuator andtransfer plate 70.

[0079] For a high production volume press, the transfer plates 70 wouldtypically be rigidly attached to the pressure actuators 28, and the topcover 32 would typically be stepped. For a low production volume press,designed to operate with a variety of molds and top covers 32, thetransfer plates 70 could be pivotably attached to the pressure actuators28. Such a pivotable attachment could include a biasing element.

[0080] In some instances, a quick release attachment mechanism to couplethe transfer plates 70 to the pressure actuators 28 may be desirable.

[0081] The benefits of the process of the present invention may berealized even when fairly large zones 30 are used to assist in theinfusion of resin 34 through the preform 24. This might be particularlytrue for larger parts 38, parts 38 with very mild curvatures, or parts38 with low fiber volume fractions. In these cases, zone groups might bedefined, wherein each zone group consists of a plurality of zones 30, acontinuous top cover portion, and a plurality of spaced pressureactuators 28. Within each zone group the areas in near proximity to apressure actuator 28 would be locally stiff, but areas not in nearproximity to the pressure actuators 28 would be somewhat more flexible.With several actuators across any one zone group, the zone group couldbe lowered all at once, or the pressure actuators 28 could besequentially actuated to “roll” down across the surface of the part 38being molded. Because the pressure actuators 28 within a zone groupcould be spaced apart, this technique would decrease the number ofrequired actuators, but still give dynamic control of the resin 34 alongmore than one axis. This technique can be taken one step further, to thepoint where the actuators 28 could be attached directly into the topcover 32. As described above, the top cover 32 is typically flexibleenough to allow for resin reservoir movement between the top cover 32and the preform 24, but stiff enough to transmit the pressure needed forinfusing resin 34 through a high fiber volume fraction preform.

[0082] During operation, the pressure actuators 28 must provide enoughpressure to compact the preform 24 to its final fiber volume fraction,but not so high a pressure that it damages the preform 24. Zone size(area) and slope determine the axial output load of any given actuator28. For a given axial output load, zones 30 that are sloped, i.e., zoneswith a normal to the surface that is at an angle to the central axis ofthe pressure actuator 28, will experience a lower pressure than zones 30that are flat. Therefore, relative to zones that are flat, zones thatare sloped will require a higher axial output load from the pressureactuator to reach the desired final fiber volume fraction. Thus,actuators having different output load capacities may be required toachieve a uniform fiber volume fraction throughout the finished part 38.Alternatively, finished parts having varying fiber volume fractionscould be specifically designed and easily manufactured using the processof the present invention.

[0083] Moreover, applying pressure to zones 30 that are sloped willcause side loads to develop in the pressure actuators 28. The magnitudeof these side loads is generally a function of the applied axial loads,the slope of the upper surface 44 of the top cover 32 or of the preform24 or molded part 38, and the mechanisms used to couple the top of thepressure actuators 28 to the platen 60 and the bottom of the pressureactuators 28 to the top cover 32 or to each other. The pressureactuators 28 must be sized and designed to adequately carry these sideloads.

[0084] Different mechanisms may be used for applying pressure to thepart 38. The method outlined thus far has dealt mostly with a pressureactuators 28 applying a pressure to the preform 24, either directly orthrough a top cover 32. However, within the scope of the presentinvention, any other suitable mechanism may also be used. For instance,pressure could also be applied using inflatable bags that areappropriately sized and shaped, and which apply the pressure uponinflation.

[0085] Although the process of the present invention could be used withmany forms of an actuated upper mold surface, the preferred actuationsystem incorporates a pneumatic solution. Compared to conventionalprocesses, the process of the present invention is a low pressuremolding operation. In general, pneumatic devices are typically cheaperand cleaner than hydraulic devices. The main drawbacks with usingpneumatics would be generating sufficient pneumatic pressure to operatethe pressure actuators at the required infusion and molding pressures,accepting larger pressure transients in the system, and compromising onthe drastically rising costs of valves which can handle both higherpressures and flow rates. For instance, in order to achieve a typicaldesign constraint of 400 psi pressure applied to the preform via thepressure actuator transfer plate, a considerably higher pneumaticpressure is needed in the actuating cylinder. Valves that canaccommodate such high pneumatic pressures, such as 2-way 3-portdirectional solenoid valves or proportional servo valves are expensive.

[0086] An alternative to using such high pneumatic pressures is amulti-cylinder pneumatic cylinder design where several pistons areattached to a common shaft in a cylinder, thereby trading increasedcylinder height for increased output force. For instance, a cylinderwith four pistons running on 150 psi air can have the output force of acylinder running on 550 psi air. One drawback is that it would bedifficult to package a multi-cylinder pneumatic cylinder design into aproduction press, as the tall cylinders would take up too much space andresult in higher bending loads on the press 10 itself. Another drawbackof the pneumatic actuator is that when the actuator must travel acertain distance before coming into contact with the top cover orpreform and applying the desired pressure, the volume of the cylinderthat must be filled to make contact is filled with high pressure airwhich is doing no work. This inefficiency would greatly increase the airconsumption of the process.

[0087] An alternative to implementing an all-pneumatic solution is toshift to the use of hydraulics. With hydraulics, the increased pressuresavailable mean that no force multiplication would be needed, and thepackaging of the actuator would be simplified. One embodiment couldinvolve the integration of the bearing surface and the hydrauliccylinders into the actuators. The outer diameter of the inner cylinderswould function as a plain bearing, sliding inside a ground cylinder thatis attached to the moving actuator surface. This embodiment would resultin a considerable amount of bearing area and minimal bending moments,solving one of the main problems encountered in use of very tall, highforce pneumatic actuators.

[0088] The problem with an all-hydraulic solution is the need forcontrolled pressure in the actuator over its travel range. This is easyto achieve with pneumatics, as air is a compressible media and a smallchange in travel results in only a small change in pressure. With ahydraulic cylinder a small change in the position of the piston canresult in the pressure in the cylinder dropping to zero (since thehydraulic fluid does not expand), making it very difficult to maintain acontrolled pressure over the full stroke if the desired actuatorpressure differs from the supply pressure. This problem is usuallyaddressed with the use of a hydraulic accumulator, which simply consistsof a pneumatic pressure source acting upon a hydraulic fluid reservoir.

[0089] A hybrid pneumatic/hydraulic system 80, as shown in FIG. 1, wasdesigned to provide efficient hydraulic power at the correct pressures.Because the bulk of hydraulic fluid supplied to an actuation cylinder 82of the pressure actuator 28 would serve only to move the actuatortransfer plate 70 into contact with the top cover 32 or preform 24, adual pressure system could be used. A low pressure pump 84 could be usedto move the actuator plate 70 into contact with the top cover 32 orpreform 24. When this occurs the system 80 would then switch to the highpressure supply. High pressure fluid (up to 2000 psi) could come from apneumatic booster arrangement. Two cylinders could be coupled together,the first, a pneumatic cylinder 86, which actuates upon the second, ahydraulic cylinder 88. Thus, for instance, if the area ratio is 20:1, aboosting 100 psi shop air could result in a 2000 psi hydraulic pressure.The resulting system would provide the compact actuation of hydraulicswith the precise pressure control of the pneumatics. The two stagehydraulic system would also provide for increased efficiency, as highpressure fluid would not be wasted in moving the actuators into contactwith the top cover 32 or preform 24.

[0090] Lower Mold

[0091] Concerns regarding the design and fabrication of the lower mold20 used in the process of the present invention are similar to theconcerns for the molds used in the SMC process. Stiffness of the mold isa key issue that impacts both the geometry of the mold and choice ofmaterial. Hardness of the mold material is another key concern whendesigning for large production volumes. Heat transfer capacity throughthe mold surface is important, as the lower mold 20 will generally beuse for thermal control of the process. Compatibility of the moldmaterial with the resin systems is also a concern, and although atypical steel mold is generally compatible with most resins, other moldmaterials could cause problems. Finally, as with all molds, cost, easeof manufacture, and availability of materials are also importantconsiderations.

[0092] Typically, temperature control systems are designed andmanufactured right into conventional molds, and the lower mold 20 of thepresent invention is no exception, in that the lower mold is the mostlikely avenue for the addition and/or removal of heat during theinfusion and/or curing processes. A variety of techniques could be usedto provide the lower mold 20 with temperature control. For instance,steel, metal, or other machinable molds could be provided with interiormachined cooling lines. Alternatively, temperature control could beprovided by cross-drilling honeycomb backing material. The sandwichconstruction, typically, aluminum honeycomb, adds stiffness relative toa solid plate having the same weight, and cooling or heating air couldbe passed through the cross-drilled passages to aid in heat transfer.Other temperature control schemes generally known to persons of ordinaryskill in the art could also be suitable.

[0093] The curvature of the mold affects many other aspects of the press10. In general, a mold having less steep slopes or curvatures isdesirable. As curvature increases, the effective area of a zone 30increases, so that the pressure applied to the preform 24 by a givenforce in the pressure actuator 28 decreases. Additionally, a steeperslope creates higher side loads on the actuator as well as thesurrounding zones. Greater curvature also increases the chance forslippage against, or smearing of the top cover 32 by the pressureactuators 28, as discussed above.

[0094] As with the top cover 32 described above, a wide variety ofsensors may be provided with the lower mold 20. Temperature, pressure,humidity and other sensors could be used to monitor and control theinfusion and curing process. Many such sensors could be mounted intomachined areas on the surface of the lower mold 20. Other sensors couldbe molded into the top cover 32, or even onto the individual pressureactuators 28. Alternatively, the sensors could simply be molded into thesurface of a composite mold.

[0095] Preforms

[0096] The process of the present invention was originally conceived toaddress problems with infusing fibrous preforms in liquid compositemolding. However, the present invention is equally valuable in allliquid molding operations and does not require that a preform 24 be usedto take advantage of its rapid resin distribution capabilities. Preformstypically consist of a fibrous reinforcement for a composite part and abinder or other agent to help the fibers maintain their shape andorientation during handling. A preform may also contain surface veils,inserts, cores, ribs, or any other items needed in the final part.

[0097] The process of the present invention makes no assumptions as tothe material or assembly process of the preform 24. Preforms may rangefrom porous solids to vacuum and anything in between that needs to beinfused with a liquid.

[0098] Injection of the Resin System

[0099] Injection of the resin 34 into the reservoir 36 formed betweenthe preform 24 and the top cover 32 preferably may be accomplished by aninjection machine having variable ratio capabilities. Variable ratiocapabilities give the injection machine the flexibility to inject manydifferent resin systems. Typically, the only limitation on such amachine is its ability to inject polyurethanes, which require adifferent setup than most other resins. However, the likelihood of usingpolyurethanes in a production environment is low, and a limitation onthe injection machine is not a limitation on the practice of the presentinvention.

[0100] Generally, injection of the resin 34 can be either of thereaction injection molding or resin transfer molding variety, dependingon the requirements of the resin system. The selection of a particularresin system is generally based on processing parameters, end useapplication characteristics, cost, and availability. The process of thepresent invention can accommodate almost all known resin systems: fastand slow curing resin systems, high and low viscosity resin systems,endothermic and exothermic curing resin systems, and all resin systemsin between.

[0101] In some instances, the thermal characteristics during curing of aparticular resin system may govern the required temperature capabilitiesof the mold.

[0102] Furthermore, the process of the present invention placesessentially no limitations on additives or fillers included in the resinsystem, although preferably the process will be practiced with a resinsystem having adequate mold release characteristics. Some resin systemshave excellent inherent mold release characteristics, while othersrequire additives to improve their mold release characteristics. Fillerscan reduce the cost of the resins, and other additives can drasticallyimprove the surface finish.

[0103] Preferably, a vacuum pump would be provided to evacuate the moldcavity. The location and number of vacuum ports are design variablesthat a person of ordinary skill in the art could determine. The use of avacuum pump requires that the mold cavity be sealed. As discussed above,several options exist for sealing the top cover 32 to the lower mold 20.

[0104] Also, in general, the top cover 32 will provide a seal betweenthe pressure actuators 28. However, since some implementations of theprocess of the present invention may not use a top cover 32, sealsseparate and distinct from the top cover 32 may be needed between theindividual pressure actuators 28 to prevent the resin 34 from leakingout.

[0105] Pultrusion

[0106] The process of the present invention is easily adaptable to apultrusion process. In such a pultrusion implementation of the processof the present invention, a pultrusion die could be divided into severalzone groups with each zone group segmented into zones controlled byindividual actuators. Rather than move the reservoir 36 over the preform24 as in the process of the first embodiment, in pultrusion the preform24 would be pulled past the reservoir 36. The pressure actuators 28 ineach zone group would provide similar actions as in the process asdescribed in connection with the first embodiment: preform clamping toprevent resin flow, infusion, reservoir transfer, and compaction to afinal fiber volume fraction.

[0107] The process of the present invention as applied to the pultrusionprocess could reduce the load required to pull the finished product fromthe die by either reducing the clamping load in the die or by moving thezones with the part. The lower pulling forces would allow larger crosssections with greater surface area to be pultruded.

[0108] Pulling loads are not constant in traditional pultrusion. When aroll of reinforcement material runs out, the next roll must be splicedto the end of the previous roll. To ensure continuity and strength inthe final part, the ends of the two rolls must be overlapped. Thetemporary increase in thickness due to the overlap increases the dragload through the fixed width pultrusion die. The process of the presentinvention as applied to the pultrusion process is pressure controlledrather than volume controlled and maintains constant clamping and dragloads on the part. A stable drag load allows the part to be pulled moreevenly, consistently, and predictably.

[0109] Importance of Process Variables

[0110] The advantage of the process of the present invention overcompeting production processes is its ability to more quickly producemore uniform parts of more complex shape, with denser and more complexreinforcement. To achieve this, active control over both the resin 34and preform 24 is exercised. The specific source of this control is theability to apply different pressures to different sections of thepreform 24.

[0111] The differential application of pressure to the preform 24 is thekey to controlling the flow of the resin 34. Actively controlling theflow is the only way to guarantee rapid filling of complex molds andpreforms. Moreover, active control enforces uniformity in the fillprocess. Finally, active control allows the process to be optimized inconcert with a simulation of the fill process, because it allows oneskilled in the art to force the resin 34 to flow only in easilypredictable ways.

[0112] According to Darcy's law, the factors that determine thedirection and speed of resin flow are the pressure gradient in theresin, the permeability of the medium in which the resin is flowing, andthe viscosity of the resin. Active control over the pressure applied tothe top of the preform 24 allows a large amount of control over thefirst two of these parameters, and a lesser degree of control over thethird.

[0113] Increasing the pressure applied to a zone 30 when that zone isnot fully infused but has resin 34 infusing into it from above willcreate a pressure gradient that will quickly drive the resin 34 throughthe thickness of the preform 24. Applying different pressures to twoneighboring zones 30 that are fully infused will cause resin 34 to flowbetween zones through the plane of the preform 24; quickly cycling thedirection of the in-plane pressure gradient will mix the resin 34 at thezone boundaries and could be done to prevent weld lines and otherdefects, as discussed above. There is also a natural pressure gradientbetween resin 34 and the vacuum.

[0114] The permeability of a section of preform 24 can also bemanipulated by the pressure applied to that section. This allowszone-by-zone control of the resistance the preform 24 offers to resinflow, and thus provides another, equally important mechanism forcontrolling where resin goes and when. Resin 34 can be discouraged frommoving into a dry zone by clamping down on the zone 30 with a highpressure.

[0115] These two mechanisms, the use of a pressure gradient to quicklydrive resin 34 through the thickness of the preform 24, and the clampingof a dry preform to control flow paths, are what enable the process ofthe present invention to achieve both its low cycle time and its qualitycontrol, even for complex parts. Better structural properties resultbecause the process of the present invention can infuse parts with avery high fiber volume fraction. Because zones 30 are infused throughthe thickness of the preform 24, and the infusion starts in a zone whileit is not under high pressure and thus has a high permeability, zones 30infuse quickly. Moreover, the zone 30 can be compressed to a very highvolume fraction while it is being infused.

[0116] There are several pressure related issues that must beconsidered. The pressure must be high enough to infuse resin 34 quicklyinto the preform 24. The holding pressure on dry preform zones 30 mustbe enough to render the zones relatively impermeable without damagingthe preform. The pressure applied to different zones must not differ somuch as to cause the resulting final infused preform thickness to varyto much. Variations in pressure between zones could result from the factthat a zone's projected area (to which a pressure actuator 28 appliesforce) will sometimes be different from its actual area.

[0117] Knowing the viscosity of the resin systems is important in orderto furnish physical property data to the flow simulation. Viscositydepends on temperature, shear rate (which is a function of how fast theresin is flowing, which is in turn influenced by the pressure gradientsintroduced by the actuators) and cure state.

[0118] Process Variable Ranges

[0119] The process of the present invention can support a wide rangeconditions during the molding process. Below is a table of variables andthe typical operating ranges over which the process could operate. Thistable is not meant to limit the ranges of the variables over which theprocess of the present invention could operate, but only to provide anunderstanding of typical operating ranges. Variable Range Units Pressure14-500 psi Temperature room-500 degrees F. Viscosity 1-30000 centipoisePermeability any- from the lightest veil cm² to impermeable insertsFiber Volume Fraction 10-75 percent

[0120] A high temperature version of the process is possible, if the topcover is replaced with seals between the pressure actuators. Forinstance, with a ceramic mold and ceramic pressure actuators, moltenmetals could be processed at temperatures of up to 2600° F.

[0121] For special applications, a higher pressure is possible, but thelow cost advantages of the process of the present invention begin todiminish above about 450 psi because of increased complexity and size ofthe actuation system, molds, and press.

[0122] Control System Hardware

[0123] For the process of the present invention, any system which canindividually control the pressure actuators 28 in the array of pressureactuators is sufficient.

[0124] In one embodiment, a PC-based control bus has been implemented onthe zoned pressure molding press 10 of the present invention. Asimplemented, this PC-based control bus is based on the German companyPhoenix Contact's Interbus® system. Although the control software hasbeen abstracted to an extent that the control hardware can be easilychanged at any point, the Interbus® system is probably the industrialcontrol network that is most compatible with the zoned pressure moldingof the present invention at this time. Interbus® also makes a largevariety of industrial I/O modules, PLC interfaces, motor starters, etc.that could make any future modifications to applications of the presentinvention much easier to implement. As shown in FIG. 12, the zonedpressure molding press control system hardware, could consist of acontroller card 90 and an input/output module 92 connected to andcontrolling valves, such as pressure selector valves 94 and zone on/offvalves 96. The valves, in turn, control the pressure actuators 28.

[0125] As presently implemented, the control system hardware consistssimply of a standard WINTEL® PC with an Interbus® controller card (IBSPC ISA SC/1-T) with a cable connecting it to a module with sixteen (16)digital outputs (IB STME 24 DO 16/3). This module is basically a stationwith 24V DC relays that energize by command of the controller card. Zoneactuation is achieved when solenoid valves are wired to the outputmodule. In this particular application, 24V DC solenoid valvesmanufactured by SMC were used. Multiple applied pressures were needed toproperly identify parameters that effect part quality. With the balancedspool of the NVS 3114, both pressure supply ports 98 and exhaust ports100 can be pressurized and used to select one of two preset pressures.The two pressures were set by pressure regulators, a low pressureregulator 102 and a high pressure regulator 104, and distributed to theselector valves 94 by a manifold 106. The selector valves then transferpressurized air to the NVS 3115 valves which turn the respective presszone valves on and off, supplying the load to the actuators. Alltogether, this pneumatic system allows computer control over threestates of a zoned pressure molding actuator (low, high, or off). Asimplemented, the maximum designed pressure the actuators are to apply is500 psi. Since all of the pneumatic system components on the press areonly rated to 150 psi, a pair of 3″ bore,1″ stroke Bimba cylinders werecoupled to apply 500 psi to one zone.

[0126] The Interbus® is also expected to perform other functions besidesthat of zone actuation. For instance, as implemented, a vacuum cut-offvalve 108, which supplies vacuum to the preform 24 through a port 110 inthe lower mold 20, could also be wired into the output module 92 of thepress 10. If a more automated zoned pressure molding press 10 is desiredor needed, the Interbus® system would be quite capable of alsocontrolling, among other things, the vacuum pump, press platen movement,mold loading and unloading, as well communication with robotic preformloading and part unloading stations.

[0127]FIG. 12 shows how the Interbus® controller card and output moduleare connected to the valve system to allow computer controlled switchingbetween two regulated pressures. FIG. 13 shows the presentimplementation in the zoned pressure molding test press.

[0128] This Interbus® system uses binary pneumatic valves, which makesthe Interbus® system probably the fastest available system for largenumbers of digital outputs. The Interbus® system was also consideredbecause it is compatible with any valve manufacturer, and thus does notnarrow valve selection like some of the other fieldbus systems. Theprimary known drawback with Interbus®, and any other fieldbus system, isthat the analog-to-digital conversion takes place out on the bus and isthen transported along the common communications line to the centralprocessor. This means that analog signals are restricted to low samplerates which may restrict the response of some feedback systems. Toovercome this drawback, a data acquisition system could be incorporatedwhereby the analog signal could be transported along a dedicated signalline to the processor.

[0129] A press 10 that can implement the process of the presentinvention will support a variety of sensors, including for example,those that measure: pressure, in the mold or in the actuation system;temperature; resin flow front position; and cure. The sensors could beused for diagnostic purposes, and also for active feedback during themolding and curing operations.

[0130] Control Software

[0131] The functional control program software, which will control theproduction press for implementing the process of the present invention,could contain the following logical components:

[0132] First, there could be a bus control module, i.e., a module thathandles the specifics of communicating to the press hardware via acommunications bus. For example, a module for controlling the INTERBUSbus could be provided in the press control program.

[0133] Second, there could be modules that hide the specific busoperations needed to control any particular press hardware behind morelogical operations. For example, in the press control program, therecould be a logical construct for valves, which could be used to turnvalves on or off without worrying about the exact commands that must besent over the bus in order to do that, or even what bus system is inuse.

[0134] Third, there could be a similar module to further remove thelogical operation of a press zone from the underlying hardwareoperations necessary to perform desired zone actions.

[0135] Fourth, there could be a module that handles the specifics ofconverting the analog signals from sensors into digital data. Forinstance, a module for controlling data acquisition boards could beprovided in the press control program.

[0136] Fifth, there could be a further layer of abstraction to representvarious sensors, regardless of the underlying DAQ system.

[0137] Sixth, there could be a module to handle the logging of actuationsequences and sensor data for each part that is produced.

[0138] Seventh, there could be a module that uses sensor input todetermine if the press is in working order or if it fails duringoperation.

[0139] Eighth, there could be a rich language for controlling zonestates and sensors with respect to time. Such a language would allowcontrol over individual zones and would also have higher-level commandsfor filling multi-zone regions. The language could incorporate branchingbased on sensor input, as well as repetition of action sequences.

[0140] Finally, there could be other software developed for interfacingwith infusion and/or curing simulations, generating the actuationprogram, etc.

[0141] As currently implemented, the press control software, for alab-scale zoned pressure molding, allows user:

[0142] to control the pressure applied to the part by the zoned pressureactuators manually or with a script;

[0143] to toggle the vacuum port and the vacuum pump manually or with ascript;

[0144] to log all zone movements, whether accomplished through manual orscripted control; and

[0145] to set all of the press zones to their off state in an emergency.

[0146] Also, as currently implemented, the press control software iswritten in Microsoft Visual Basic®, a computer programming language withobject-oriented features. It contains classes, which satisfy thefollowing purposes:

[0147] bus abstraction;

[0148] press component abstraction;

[0149] Script interpretation and execution;

[0150] zone logging; and

[0151] user interface.

[0152] Additionally, as presently implemented on the lab-scale zonedpressure molding press, the software contains classes that abstractlyrepresent the Interbus® controller and the Interbus® devices to whichthe press hardware is attached. The bus control classes handle allcommunications with the bus system, using the Interbus® driver to sendcommands to the Interbus® controller card. The classes make the propercalls to build the configuration frame for the connected Interbus®devices at start-up. They also write process data to the devices duringpress operation, which in turn causes the press hardware to respond. Thelab-scale zoned pressure molding press uses two Interbus® devices, theInterbus® Test Drive Kit controller and digital output module and aconventional Interbus® digital output module. It is easy to add orsubtract from the Interbus® configuration that controls the press and toreflect these changes in the software. The bus classes, whileimplemented in Visual Basic®, could easily be implemented in a varietyof languages.

[0153] Also, as presently implemented on the lab-scale zoned pressuremolding press, the software contains classes that abstractly representphysical press components: valves, zoned pressure actuators, toggleswitches for vacuum control, and the complete press itself. The classthat represents an array of valves directly uses the bus controlclasses. The class that represents an array of zoned pressure actuatorsuses the valve array class, because each zoned pressure actuator iscontrolled by individually controlling two valves. The class thatrepresents the press uses the zoned pressure actuator array and toggleswitch classes. Such abstractions are necessary because they ensurefuture control software extensibility. Moreover, because commands passthrough several layers, it is possible to make changes to how thesoftware works at different levels without impacting the entire program.It is also possible to add new hardware, such as sensors, to the zonedpressure molding press and to reflect that easily in the software. Likethe bus control classes, the press component classes could also beeasily implemented in a variety of development environments. FIG. 14 isa diagram of the distinct layers formed by the bus and press componentclasses, and the usage relationships between the classes.

[0154] Also, as presently implemented on the lab-scale zoned pressuremolding press, the software contains classes that interpret and executeZoned Pressure Molding Language (ZPML) scripts. The script interpreterclass reads a file containing a ZPML script and parses the text. Theresult is ZPML machine code, an array of integers representing commandsto be sent to the press. A separate class executes the ZPML machinecode, issuing the proper commands to the class representing the ZPMpress.

[0155] The format of a ZPML script is:

[0156] SCRIPT

[0157] [statements]

[0158] END

[0159] A statement can be either an ACTION or a WAIT. The format for aWAIT statement is:

[0160] WAIT n

[0161] where n is the number of milliseconds to wait before executingthe next statement. The format for an ACTION statement is:

[0162] ACTION {ZONES|VACUUM}

[0163] statement body

[0164] END

[0165] The statement body for an ACTION ZONES statement assignspressures to specific zoned pressure actuators, using one or more linesof the following format:

[0166] ZONE row column {OFF|LOW|HIGH}

[0167] where row and column specify the zoned pressure actuator in thetwo-dimensional zoned pressure actuator array. The row and columnindices for a zoned pressure actuator array start at zero. The statementbody of an ACTION VACUUM statement specifies which vacuum element totoggle, the port switch or the pump switch, using a line of thefollowing format:

[0168] {PORT|PUMP} TOGGLE

[0169] White space and indentation within scripts is ignored by theparser, but may be included for readability.

[0170] For instance, here is an example of a script that toggles thevacuum port, waits two seconds, and then sets the second and thirdactuators in the first row of a zoned pressure actuator array to highpressure. It should be noted that, while ZPML supports a two-dimensionalarray of zones, the lab-scale zoned pressure molding press has just onerow of five zones. Both the ZPML script and ZPML machine code aredesigned to be extensible for future press control needs. SCRIPT ACTIONVACUUM PORT TOGGLE END WAIT 2000 ACTION ZONES ZONE 0 1 HIGH ZONE 0 2HIGH END END

[0171] As implemented, the software contains classes that can log whenzones are commanded to change pressure. The user can turn the log on andoff, and save the log to a file.

[0172] Finally, as implemented, the zoned pressure molding pressincludes a user-interface. The user-interface contains controls for themanual actuation of the five lab-scale zoned pressure molding presszones and toggling the vacuum port and vacuum pump. The user can clickon the appropriate command button to set a zone to a state of “off,”“low pressure,” or “high pressure,” or to toggle the vacuum port andvacuum pump. FIG. 15 shows the Press Control Panel from theuser-interface as currently implemented. The user-interface alsocontains controls to allow the user to load, execute, or stop a scriptusing the Press Control Panel.

[0173] Practical Implementation

[0174] The zoned pressure molding process of the present invention hasbeen demonstrated on a small scale in the preparation of 2″ by 10″ testcoupons. The test press (shown in FIG. 13) consists of five actuators of2″ by 2″ size. The actuators are modular, and can have a variety ofzoned pressure actuators attached. For initial coupon production,machined blocks of mahogany were used to apply pressure to a flexibletop cover. The top cover is made of 0.030″ thick silicone rubber and issimply clamped to the mold to form a seal. The mold is a plate ofaluminum with a 2″ by 10″ channel cut out of it which has been gluedwith silicone to a 1″ thick glass plate which forms the lower half ofthe mold. The glass allows monitoring of the flow front with a videocamera.

[0175] The preforms that have been used for the initial testing are madeup of five layers of PPG 3 oz random strand mat. This material isdifficult to process to high volume fractions and is sensitive to damageby excessive pressure. It is very similar to the preforms that areexpected to be used with the zoned pressure molding process of thepresent invention for mass production. The coupon tests were used tofind the process limits for this material.

[0176] The resin used in the coupon tests is a heavily promoted, roomtemperature curing polyester system from Interplastic Resin Corporation.The system was chosen for room temperature cure to allow the use of anunheated, glass bottom mold for flow analysis, and for its very fastcuring. With the appropriate catalyst percentage, the system has a geltime ranging from 30 seconds to 8 minutes, allowing the simulation ofvery fast cycle time resins that would be used in a mass productionapplication, while also allowing slower and more careful experimentswith specific flow regimes.

[0177] A typical production run for a coupon consists of the followingsteps.

[0178] High and low pneumatic bus pressures are selected and manuallyadjusted;

[0179] Preform is prepared by cutting 2″ by 10″ strips from a roll ofmat and stacking them;

[0180] Mold is waxed to allow part release;

[0181] Appropriate resin mixture is prepared but not catalyzed;

[0182] Injector, top cover and cover plate are attached;

[0183] Vacuum pump is started;

[0184] Vacuum is created within the preform through the mold vacuumport;

[0185] Mold is loaded into the press;

[0186] Actuation sequence/recorder is loaded in the control software;

[0187] Resin is catalyzed and mixed;

[0188] Syringe is filled with mixed resin and connected to the injector;

[0189] Video camera is started;

[0190] Resin is injected through the top cover;

[0191] Injector is closed and locked;

[0192] Computerized actuation sequence is begun;

[0193] Vacuum valve is closed;

[0194] Part cures;

[0195] Actuators are released; and

[0196] Top cover is unclamped and the part is removed.

[0197] After part removal, the only preparation needed to run anothercoupon is the cleaning of the mold glass and the top cover. With asuccessful run, there is usually minimal or no residue to remove.

[0198] For a typical coupon test, the following parameters are used:

[0199] Preform: five layers PPG 3 oz random strand mat;

[0200] Resin: Interplastic CoRezyn COR 40-B2-8099;

[0201] Catalyst: 1.75% by weight Norox MEKP;

[0202] Volume of injected resin: 27 cc;

[0203] High bus pressure: 50 psi (resulting in 175 psi at the actuator);

[0204] Low bus pressure: 30 psi (resulting in 105 psi at the actuator);

[0205] Mold temperature: 72 degrees F.;

[0206] Resin temperature: 72 degrees F.;

[0207] Resin viscosity: approximately 200 centipoise; and

[0208] Gel time: 2:30 (min:sec).

[0209] The following actuation program is used to control the infusionof the test coupons. The ZPML script holds the zones not yet infused athigh pressure while the infusion of the other zones takes place. Whenshuttling the resin reservoir from one zone to another, this scriptreleases pressure in the adjacent zone and the reservoir, then reappliespressure to the reservoir to provide for a more controlled movement fromzone to zone and to minimize the pressure spikes in the pneumaticsystem. The time that the pressure is held on the reservoir at each zoneis varied to account for the increasing viscosity due to anycrosslinking of the resin. SCRIPT ACTION ZONES ZONE 0 0 LOW ZONE 0 1HIGH ZONE 0 2 HIGH ZONE 0 3 HIGH ZONE 0 4 HIGH END WAIT 2000 ACTIONZONES ZONE 0 0 OFF END WAIT 100 ACTION ZONES ZONE 0 1 OFF END WAIT 500ACTION ZONES ZONE 0 0 LOW END WAIT 8000 ACTION ZONES ZONE 0 1 LOW ENDWAIT 2000 ACTION ZONES ZONE 0 1 OFF END WAIT 100 ACTION ZONES ZONE 0 2OFF END WAIT 500 ACTION ZONES ZONE 0 1 LOW END WAIT 10000 ACTION ZONESZONE 0 2 LOW END WAIT 3000 ACTION ZONES ZONE 0 2 OFF END WAIT 100 ACTIONZONES ZONE 0 3 OFF END WAIT 500 ACTION ZONES ZONE 0 2 LOW END WAIT 12000ACTION ZONES ZONE 0 3 LOW END WAIT 4000 ACTION ZONES ZONE 0 3 OFF ENDWAIT 100 ACTION ZONES ZONE 0 4 OFF END WAIT 500 ACTION ZONES ZONE 0 3LOW END WAIT 16000 ACTION ZONES ZONE 0 4 LOW END WAIT 2600 ACTION VACUUMPORT TOGGLE END END

[0210] The result is a part cured to 58-64% volume fraction, havingtensile strength ranges from 40-50 ksi and modulus from 2.5-3.2Msi.These are all extremely good values for random strand mat and polyesterresin.

[0211] Factors Affecting the Process

[0212] One of the benefits of the process of the present invention isthat it is a composite liquid molding process, and thus, in terms ofpress hardware, the press loads are greatly reduced over almost allother non-liquid molding press operations. Hardware costs are reduceddue to the reduction in platen size and the lower cost of the pressureactuators. However, with the process of the present invention, many verysmall independent actuators are required. Thus, the reduced hardwarecost comes at the price of increased process complexity. The infusionprocess is no longer a simple on/off operation, but now involvesspecific pressure actuator sequences, possibly with many changes in theloads applied by each actuator during any given process cycle.

[0213] On the other hand, this increased control complexity can betransformed into increased process control. The application of a givenpressure at a given point during the process can depend on manydifferent factors. These factors can be grouped into four basic groups,all of which are, to some extent, governed by the specific resin infusedinto the preform.

[0214] The first group of factors is primarily concerned with fibervolume fraction control. Ease of reservoir movement can be facilitatedwith very small, if not zero, pressure, but the infusion and finalholding pressure can easily reach aerospace autoclave pressures. Inspecific zones constant pressure on the reservoir could be maintained toaccount for reservoir loss through induced RTM-type flows, i.e., flowsthrough the plane of the preform. Neighboring zones could maintain alower pressure to increase porosity and decrease infusion time in thoseRTM areas. Constant pressure boundary conditions could also assist inretaining a proper load during part shrinkage.

[0215] The second group of factors is primarily concerned with thetrade-offs between process speed and preform damage. The resin reservoircan be moved easily around above the preform by releasing the pressure,possibly to zero, in the zone or zones where the resin reservoir isdesired, while maintaining or supplying pressure to the zones where theresin reservoir is not desired. Duration of infusion through thethickness direction can be reduced by increasing the pressure applied tothe zones containing the resin reservoir. Preferably the zones adjacentthe reservoir zones maintain some pressure to hold the preform in place,decreasing the porosity in these adjacent zones and inhibiting RTM-typeflow, and thereby keeping the resin reservoir from moving out of itscurrent zones. This load on the neighboring “dry” zones may need to belimited so that the preform, whether the individual fibers or thepreform architecture, for instance, is not damaged. Although the preformin the reservoir zones is under a higher pressure, it is loadedhydraulically and thus, would not be damaged as easily as the “dry”preform. Also, after infusion, the final holding pressure may need to belimited so as not to damage the preform. In any case, cycle time couldbe decreased by increasing the applied pressure in certain areas and atcertain stages of the process, limited by preform and correspondinglyfinal part damage.

[0216] The third group of applied pressure parameters is concerned withthe preform type. Glass or carbon fiber, impermeable cores, variousgeometries, etc. can all be accommodated within the process of thepresent invention. The specific application of the process of thepresent invention will determine the actuation scheme. Dry preformholding pressures can differ depending on the strength of the preform.Furthermore, the viscosity of the unfused resin may require increasedreservoir pressures for through-thickness infusions and to induceRTM-type flows. RTM-type flows could also be used to infuse beneathimpermeable cores, inserts, and other special inclusions. Largevariations in the properties of the preform and the correspondingly widerange of desirable applied pressures could also be accommodated usingthe process of the present invention due to the array of independentlycontrollable actuators. Although large preform variances would notnecessarily lead to cost effective manufacturing, the process of thepresent invention would still able to accommodate them.

[0217] The fourth pressure parameter group would be those parametersspecific to a given mold. This group would include factors such as theincrease in applied surface area, and the corresponding reduction inapplied pressure for a given axial load in a pressure actuator, due tocurvature of the mold. The contours of a mold also create side thrustloads between neighboring pressure actuators, thereby increasing thefrictional loads between actuators, and possibly causing pressureactuator bearings to seize or even drastic misalignments of the pressureactuator's transfer plates.

[0218] Layout of a Press

[0219] The layout of a press for practicing the present invention willbe primarily determined by the specific implementation of the press inthe production setting. Some of the features that may vary could be theactuator design, the mold, robotic loading and unloading, temperatureregulation and resin injection equipment, and possibly platen motionequipment. The actuators simply include mechanisms that apply loads to atop cover or directly to the reservoir. The actuators could behydraulic, pneumatic, solenoid, or any other mechanism that could applythe correct loads to the reservoir and preform. Robotics may be used forpreform loading and part unloading. The actual implementation may dependon whether or not the mold moves in and out of the press. This may alsocomplicate the mold temperature regulation equipment which might have tobe coupled to the mold after it has been loaded into the press.Similarly, moving the mold into and out of the press would alsocomplicate the injection equipment. In either case, the upper and/orlower platens may need to be mechanically separated so that the robotswould have access to the mold or the mold would have enough clearance tomove in and out.

[0220] There are some additional items which may be desired depending onthe specific application. Depending on which actuator type is chosen,intermediate platens may be desired to accommodate bearings. Suchbearings may be desired to react the side thrust loads created by thepressure actuators acting upon contours of the mold. Intermediateplatens may also be desired to hold the pneumatic or hydrauliccylinders, the valves, and/or the plumbing of the pressure actuators.

[0221] If the mold is a permanent fixture of the press, a top covercould be lowered and held in place on the mold. This may require, forinstance, a separate actuator with a locking device.

[0222] Even other embodiments of the invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein.

[0223] It is intended that the specification and examples be consideredas exemplary only, with a true scope and spirit of the invention to beindicated by the claims.

I claim:
 1. A machine for molding a part having first and secondsurfaces from a raw material, comprising: a first mold having a surfacethat defines the first surface of the molded part; and a second moldhaving a platen and a plurality of pressure actuators extendingtherefrom and defining the second surface of the molded part, each ofthe plurality of pressure actuators capable of applying a pressure tothe raw material; wherein at least two of the pressure actuators arenested.
 2. The machine of claim 1, wherein at least one of the pluralityof pressure actuators is capable being actuated substantiallyindependently of the other pressure actuators.
 3. The machine of claim1, wherein at least one of the plurality of pressure actuators includesa transfer plate.
 4. The machine of claim 1, wherein at least one of theplurality of pressure actuators includes a pad.
 5. The machine of claim1, wherein a controller controls each of the plurality of pressureactuators.
 6. A machine for molding a part having first and secondsurfaces from a raw material, comprising: a first mold having a surfacethat defines the first surface of the molded part; a second mold havinga platen and a plurality of pressure actuators extending therefrom anddefining the second surface of the molded part, each of the plurality ofpressure actuators capable of applying a pressure to the raw material;and at least a first seal located between a sliding surface of a firstpressure actuator and a sliding surface of a second pressure actuator.7. The machine of claim 6, wherein at least one of the plurality ofpressure actuators is capable being actuated substantially independentlyof the other pressure actuators.
 8. The machine of claim 6, wherein thefirst pressure actuator includes a first transfer plate, wherein thesecond pressure actuator includes a second transfer plate, and whereinthe first seal is located between the first and second transfer plates.9. The machine of claim 6, wherein the sliding surface of the firstpressure actuator includes a channel and the first seal is located atleast partially within the channel.
 10. The machine of claim 6, whereinthe first seal is a substantially vacuum tight seal.
 11. The machine ofclaim 10, wherein the first seal is one of an elastomeric seal and apolymeric seal.
 12. The machine of claim 6, wherein the first seal is asubstantially resin tight seal.
 13. The machine of claim 12, wherein thefirst seal is one of an elastomeric seal, a polymeric seal, and abraided compression seal infused with a polymer.
 14. The machine ofclaim 9, further including a second seal located between the slidingsurface of the first pressure actuator and the sliding surface of thesecond pressure actuator, wherein the sliding surface of one of thefirst pressure actuator and the second pressure actuator includes asecond channel and the second seal is located at least partially withinthe second channel.
 15. The machine of claim 14, wherein a sealenergizing ring is located at least partially within the second channel.16. A method for manufacturing a molded part in a press, the methodcomprising: providing the machine of claim 6; positioning a preformhaving a thickness in the first mold; placing a quantity of resinadjacent the preform, creating a resin reservoir; selectively actuatingone or more of the plurality of pressure actuators to apply pressure tothe resin reservoir to force at least a portion of the resin reservoirto infuse through the thickness of the preform; curing the resin-infusedpreform; and removing the cured resin-infused preform from the press.17. The method of claim 16, wherein the step of selectively actuatingincludes selectively actuating one or more of the plurality of pressureactuators to apply pressure to the preform adjacent to that portion ofthe preform being infused through the thickness with resin.
 18. Themethod of claim 16, wherein the step of selectively actuating includesselectively activating one or more of the plurality of pressureactuators to increase and decrease the pressure on at least a portion ofthe resin infused preform.
 19. A method for manufacturing a moldedstructure, the method comprising: providing the machine of claim 1;placing a quantity of a raw material into the first mold; selectivelyactuating one or more of the pressure actuators apply pressure to theraw material to force at least a portion of the raw material to conformto the first mold; curing the raw material to form a cured part; andremoving the cured part from the first mold.
 20. The method of claim 19,wherein the raw material includes a preform and a quantity of resin, thepreform having a thickness and the quantity of resin forming a reservoiradjacent to the preform.
 21. The method of claim 19, wherein the step ofselectively actuating forces at least a portion of the resin to infusethrough the thickness of at least a portion of the preform.